If you leave the unit on, even if it's in a sleepy state, it still takes some power. Not the screen though, but the processor needs power to be alive. Turning it off means it uses absolutely no power (other than maybe an internal clock?), and only the self-discharge of the battery occurs. I think someone said that turning the unit off and on again takes as much battery as ~15 minutes of idle time...

I see. In that case it'd be good to know just how much different operations impact the battery. If ~15 mins of idle state is as much as turning it off and on, then idle state eats a lot. Oh well, people can always test for themselves I guess.

If ~15 mins of idle state is as much as turning it off and on, then idle state eats a lot.

... or turning it off and on doesn't eat so much Let's say it updates the screen 4 times. If 4 refreshes equal 15 minutes, the claimed 8000 refreshes of battery life would equal 500 hours, that's almost three weeks of idling...

Is this really an issue? If it takes nearly a week to discharge it seems to me that you will get years of use of the battery.

I meant the time it takes the battery to discharge, not the time it takes the battery to be dead and useless and not accepting charge anymore. The latter is indeed several years, I've had my Cybook for more than two years, and the battery is still healthy.

I meant the time it takes the battery to discharge, not the time it takes the battery to be dead and useless and not accepting charge anymore. The latter is indeed several years, I've had my Cybook for more than two years, and the battery is still healthy.

Yes, but it will loose capacity even if you do not use it. So the important factor is if keeping it always on really will decrease the capacity significantly faster. I doubt it.

Yes, but it will loose capacity even if you do not use it. So the important factor is if keeping it always on really will decrease the capacity significantly faster. I doubt it.

I think it actually will.

There are two factors which "age" a Lithium Ion battery:

1. A "natural" decay, which starts the first time it's charged. Typically a LiIon battery has a "lifetime" of perhaps 5-7 years.

2. A "charge cycle" decay. As well as its "natural" lifetime, the battery will lose a small amount of charge capacity for each charge cycle it goes through.

Item 1 will not be affected by leaving the CyBook turned on, but item 2 will, because you'll be charging it more often. After a year or two, a Cybook that's permanently turned on, and charged once a week, will almost certainly have a lower battery capacity than one that's turned off every night, and hence only goes through a charge cycle once a month.